@ed111 When using the Deco mesh, did you disable the wifi of the Fritz!Box router? Or, at a minimum, use another name for the router wifi and the Deco wifi?

@PH99 When you do the setup of a Deco network, you define the main Deco, the attribute of the network, then you add satellite Decos to the network. The Deco will automatically chose the most...

@Alexandre. As long as it is not restarted, acting as a DHCP server and as a LAN gateway should not prevent the Deco to detect that Internet is reachabe again, just like a Deco in router mode does....

@Alexandre. If the Deco could be configured with a static IP in AP mode, the Deco would promptly detect that Internet is reachable, and would immediately stop acting as a DHCP server.

@Alexandre. If the main Deco is not bounced, will it answer to DHCP requests from its WAN port?

@Alexandre. I assume that, in the scenario you describe, the ISP router detected another active DHCP router because the Deco forgot where was its WAN port, and acted as a DHCP server on that WAN port...